Miniature pump for liquid cooling system

ABSTRACT

A miniature pump in accordance with the present invention comprises a pump casing ( 10 ) and a liquid circulating unit ( 20 ) received in the pump casing. The pump casing comprises a hollow main body ( 14 ) transversely forming a spacing plate ( 126 ) and a partition wall ( 144 ) spaced from the spacing plate. The liquid circulating unit comprises a shaft ( 25 ) mounted between the partition wall and the spacing plate, a bearing ( 27 ) rotatably mounted the shaft, an impeller ( 26 ) attached to the bearing, a first pair of spaced magnetic spacers ( 21,22 ) surrounding an upper portion of the shaft and positioned above the bearing, and a second pair of spaced magnetic spacers ( 23, 24 ) surrounding a lower portion of the shaft and positioned below the bearing. The two pairs of magnetic spacers properly suspend the impeller in a stable position in an axial direction of the pump when the impeller rotates.

FIELD OF THE INVENTION

The present invention relates generally to pumps, and more particularly to a miniature pump having a magnetically levitated impeller for a liquid cooling system for cooling an electronic package.

DESCRIPTION OF RELATED ART

With the continued development of computer technology, electronic packages such as the CPUs are generating more and more heat that needs to be dissipated immediately to avoid damage to the circuitry. Conventional heat dissipating devices such as heat sink/fan combinations are not sufficiently effective at dissipating heat to cope with modern circuitry. Liquid cooling systems have thus been increasingly used in computer technology to cool these electronic packages.

A typical liquid cooling system comprises a heat absorbing unit for absorbing heat from a heat source, and a heat dissipating unit which is filled with liquid. The liquid exchanges heat with the heat absorbing unit, thereby taking away the heat of the heat absorbing unit as the liquid is circulated. Typically, a pump is used to circulate the liquid.

Generally, the pump comprises a housing having a bottom plate, a shaft having a bearing pivotably attached thereto, an impeller received in the housing and attached to the bearing, a magnetic coupling structure, and a motor. The shaft passes through the impeller and engages with the bottom plate of the housing. The magnetic coupling structure comprises an inner magnet mounted on the impeller and an outer magnet appropriately disposed on the motor outside of the pump housing. In operation, the motor rotates to drive the outer magnet to rotate therewith. The inner magnet receives the attractive force of the outer magnet, so that the inner magnet is caused to rotate at a high speed as a result of the high-speed rotation of the outer magnet, thus causing the impeller to rotate with high-speed. The impeller thus rotates with the inner magnet to circulate the liquid in the liquid cooling system, thereby taking away the heat. However, a problem existing in the conventional pump is that during the high-speed rotation of the pump there is friction between a bottom of the bearing and the bottom plate of the housing of the pump because the axial attract force of the outer magnet is applied on the impeller having the inner magnet, which causes damage to the pump housing. A way of reducing the friction between the bearing and the pump housing is that a wearable washer is mounted between the bearing and the bottom plate of the pump housing, however this can result in high levels of unwanted noise pollution.

Therefore, there is a need for a pump with a low-friction bearing

SUMMARY OF INVENTION

According to a preferred embodiment of the present invention, a miniature pump comprises a pump casing and a liquid circulating unit received in the pump casing. The pump casing comprises a hollow main body transversely forming a spacing plate and a partition wall separated from the spacing plate. The liquid circulating unit comprises a shaft mounted between the partition wall and the spacing plate, a bearing rotatably mounted mounted to the shaft, an impeller attached to the bearing to rotate therewith, a first pair of spaced magnetic spacers surrounding an upper portion of the shaft and positioned above the bearing, and a second pair of spaced magnetic spacers surrounding a lower portion of the shaft and positioned below the bearing. The two pairs of magnetic spacers suspend the impeller in a stable position in an axial direction of the pump when the impeller rotates so that the impeller is prevented from rubbing against the partition wall when the impeller rotates.

Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded, isometric view of a miniature pump according to a preferred embodiment of the present invention;

FIG. 2 is an assembled view of the miniature pump of FIG. 1; and

FIG. 3 is a cross sectional view taken along line III-III of FIG. 2.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a miniature pump in accordance with a preferred embodiment of the present invention comprises a pump casing 10 having an inner space, and a liquid circulating unit 20 and a motor driving unit 30 received in the inner space of the pump casing 10.

The pump casing 10 comprises a hollow main body 14, a top cover 12 hermetically attached to a top end 140 of the main body 14, and a bottom cover 16 attached to a bottom end 143 of the main body 14. A sealing ring 141 is disposed between the main body 14 and the top cover 12 to prevent liquid leakage. The top cover 12 forms an annular groove 120 at a bottom edge thereof for receiving the sealing ring 141 therein. An inlet 122 is formed on the top cover 12 for allowing liquid to enter the pump casing 10. An outlet 142 is formed on the main body 14 for allowing the liquid to exit the pump casing 10.

The main body 14 transversely forms an inner partition wall 144. This partition wall 144 effectively divides the inner space of the main body 144 into a top space 146 and a bottom space 148.

Referring also to FIG. 3, a spacing plate 126 is transversely arranged in the main body 14 as a guide means. The spacing plate 126 further divides the top space 146 of the main body 14 into a first chamber 145 between the spacing plate 126 and the top cover 12, and a second chamber 147 between the partition wall 144 and the spacing plate 126. A round cap 1260 protrudes upwardly from a center of the spacing plate 126. A protrusion 1262 having an inner space communicating with the cap 1260 protrudes from a top of the cap 1260. A plurality of through openings 1264 is defined in the spacing plate 126 adjacent to the cap 1260 to intercommunicate the first and second chambers 145, 147.

Referring to FIGS. 1 and 3, the liquid circulating unit 20 is mounted in the second chamber 147 of the pump casing 10. The liquid circulating unit 20 comprises a shaft 25 mounted between the partition wall 144 and the spacing plate 126, a bearing 27 pivotably attached to the shaft 25 and a magnetically levitated impeller 26 attached to the bearing 27. A first permanent magnet 261 is embedded in the impeller 26. The first permanent magnet 261 has a substantially ring-shaped flat body magnetized so as to have a plurality of alternating N and S poles along the ring body. The impeller 26 comprises a center hollow post 260 having a receiving room and a plurality of alternating first and second blades 262, 263, wherein the first blades 262 extend from the center post 260 to an outer edge portion of the impeller 26, and the second blades 263 are formed at the outer edge portion of the impeller 26. For positioning the shaft 25, the partition wall 144 forms a shaft support 1440 having a center blind hole 1442 receiving a bottom end of the shaft 25 therein, and a top end of the shaft 25 engages in the inner space of the protrusion 1262 of the spacing plate 126. An annular recess 1444 communicating with and surrounding the blind hole 1442 is defined in the shaft support 1440.

The motor driving unit 30 is received in the bottom space 148 of the pump casing 10. The motor driving unit 30 is positioned on the bottom cover 16 and comprises a motor having a rotor 32. A second permanent magnet 320 is attached to the rotor 32 for rotating therewith, in a position corresponding to that of the first permanent magnet 261 with a flux gap formed therebetween. Like the first permanent magnet 261, the second permanent magnet 320 also has a ring flat body magnetized so as to have a plurality of alternating N and S poles along the ring body.

In operation, the rotor 32 of the motor driving unit 30 rotates so as to drive the second permanent magnet 320 to rotate therewith. The first permanent magnet 261 is driven to rotate with second permanent magnet 340 by the attractive magnetic force therebetween. The impeller 26 thus rotates with the first permanent magnet 261 to circulate the liquid in the liquid cooling system. In the present invention, the impeller 26 uses four annular magnetic spacers 21-24 to control its axial position, wherein the magnetic spacers 22, 23 are received in two opposite ends of the impeller 26 and rotate with the impeller 26, the magnetic spacers 21, 24 are respectively fixedly received in the spacing plate 126 and the partition wall 144. The magnetic spacers 21, 22 surround an upper portion of the shaft 25 without connection therewith and are positioned above the bearing 27. The magnetic spacers 21, 22 are spaced and opposite to each other, wherein the magnetic spacer 21 is received in the cap 1260 of the spacing plate 126 and the magnetic spacer 22 is received in an upper portion of the receiving room of the post 260. Each of the magnets 21, 22 has a north (N) pole and an opposite south (S) pole. The magnetic spacers 21, 22 are arranged so that the S pole of the magnetic spacer 21 opposes the S pole of the magnetic spacer 22. The like magnetic poles oppose each other so that a repulsive force F1 exists between the magnetic spacers 21, 22, which means the impeller 26 with the magnetic spacer 22 is pushed downwards with force F1 by the magnetic spacer 21. When the impeller 26 rotates, the impeller 26 acts on the liquid with centrifugal force. Simultaneously, the liquid acts on the impeller 26 with a corresponding force F. The force F has an upward component F4 where the liquid acts on the impeller 26 in an axial direction. The magnetic spacers 21, 22 are used to provide the downward force F1 to the impeller 26 to balance the upward axial force F4. The magnetic spacers 23, 24 surround a lower portion of the shaft 25 without connection therewith and are positioned below the bearing 27. The magnetic spacers 23, 24 are located so as to be separate and opposite to each other, the magnetic spacer 23 is received in a lower portion of the receiving room of the post 260 and the magnetic spacer 24 is received in the recess 1444 of the shaft support 1440. Each of the magnetic spacers 23, 24 has an N pole and an opposite S pole. The magnetic spacers 23, 24 are arranged so that the S pole of the second magnetic spacer 23 opposes the S pole of the magnetic spacer 24. Since like magnetic poles oppose each other so that a repulsive force F2 exists between the second magnets 23, 24, and the impeller 26 has an upward force F2 exerted on it by the magnetic spacer 21. When the impeller 26 rotates, an axial component force F3 pushes downward on the impeller 26 because of a magnetic interaction between the first permanent magnet 261 and the second magnet 320 of the motor driving unit 30. The magnetic spacers 23, 24 are used to provide the upward force F2 to the impeller 26 to balance the downward axial force F3 and the force G of gravity acting on the impeller 26. When the impeller 26 operates, total axial force acting on the impeller 26 is balanced, wherein the total axial force is illustrated by following equation: F1+G+F3=F2+F4. The four magnetic spacers 21-24 properly suspend the impeller 26 in a stable position in the axial direction such that a bottom of the impeller 26 has no contact with the partition wall 144, whereby a friction between the bottom of the impeller 26 and the partition wall 144 is prevented and noise pollution is considerably reduced.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A miniature pump for use with a liquid cooling system, comprising: a pump casing comprising a hollow main body transversely forming a spacing plate and a partition wall below and spaced from the spacing plate; and a liquid circulating unit received in a receiving space between the spacing plate and the partition wall for circulating liquid in the liquid cooling system, the liquid circulating unit comprising a shaft fixedly mounted between the partition wall and the spacing plate, a bearing mounted to the shaft and rotatable in respect thereto, an impeller attached to the bearing to rotate therewith, a first pair of spaced magnetic spacers surrounding an upper portion of the shaft and positioned above the bearing, and a second pair of spaced magnetic spacers surrounding a lower portion of the shaft and positioned below the bearing; wherein the two pairs of magnetic spacers suspend the impeller in a stable position in an axial direction of the shaft when the impeller rotates so that the impeller is prevented from rubbing against the partition wall when the impeller rotates.
 2. The miniature pump as described in claim 1, wherein one of the first pair of magnetic spacers is received in the impeller, and the other one of the first pair of magnetic spacer is received in the spacing plate.
 3. The miniature pump as described in claim 1, wherein one of the second pair of magnetic spacers is received in the impeller, and the other one of the second pair of magnetic spacers is received in the partition wall.
 4. The miniature pump as described in claim 1, wherein each of the magnetic spacers has a north pole and an opposite south pole, the first pair of magnetic spacers have same poles at opposing surfaces thereof so that a repulsive force exists between the first magnetic spacers, and the second pair of magnets have same poles at opposing surfaces thereof so that a repulsive force exists between the second pair of magnetic spacers.
 5. The miniature pump as described in claim 1, wherein the spacing plate defines a through opening for allowing the liquid to enter the receiving space.
 6. The miniature pump as described in claim 1, wherein the partition wall forms a shaft support defining a center blind hole and a recess surrounding and communicating with the blind hole, an end of the shaft is received in the blind hole, and one of the second pair of magnetic spacers is received in the recess, and the spacing plate forms a cap and a protrusion having an inner space communicating with the cap, an opposite end the shaft is received in the protrusion, and one of the first pair of magnetic spacers is received in the cap.
 7. The miniature pump as described in claim 6, wherein the impeller comprises a center hollow post having a receiving room and a plurality of blades, the other one of the first pair of magnetic spacers is received in an upper portion of the receiving room, and the other one of the second pair of magnetic spacers is received in a lower portion of the receiving room.
 8. The miniature pump as described in claim 7, wherein the blades of the impeller comprises alternating first and second blades, the first blades extend from the center post to an outer edge portion of impeller and the second blades are formed at the outer edge portion of the impeller.
 9. The miniature pump as described in claim 1, further comprising a motor driving unit received in the pump casing below the partition wall for driving the impeller of the liquid circulating unit to rotate.
 10. The miniature pump as described in claim 9, wherein the impeller carries a first permanent magnet, the motor driving unit comprises a motor having a rotor, and a second permanent magnet is attached to the rotor corresponding to the first permanent magnet.
 11. The miniature pump as described in claim 10, wherein the first permanent magnet is embedded in the impeller.
 12. The miniature pump as described in claim 10, wherein each of the first and second permanent magnets comprises a ring-shaped flat body, and an axial flux gap is created between the first and second permanent magnets.
 13. A liquid pump for use with a liquid cooling system, comprising: a pump casing comprising a spacing plate having a first magnetic spacer and a partition wall having a second magnetic spacer both transversely formed therein to form an inner space between the spacing plate and the partition wall for receiving a magnetically levitated impeller therein, the impeller having a pair of third magnetic spacers, one of the third magnetic spacers of the impeller being received in an upper portion of the impeller and being opposite to the first magnetic spacer of the spacing plate, and the other one of the third magnetic spacers of the impeller being received in a lower portion of the impeller and being opposite to the second magnetic spacer of the partition wall; and a motor driving unit positioned outside of the inner space to drive the impeller to rotate; wherein when the impeller is rotated by the motor, the impeller is suspended between the spacing plate and the partition wall and total axial force to the impeller is balanced.
 14. The liquid pump as described in claim 13, wherein each of the first, second and third magnetic spacers has a north pole and an opposite south pole, the first magnetic spacer and the one of the third magnetic spacers have same poles at opposing surfaces thereof so that a repulsive force exists therebetween, the second magnetic spacer and the other one of the third magnetic spacers have same poles at opposing surfaces thereof so that a repulsive force exists therebetween.
 15. The liquid pump as described in claim 14, wherein the impeller carries a first permanent magnet, the motor driving unit comprises a rotor and a second permanent magnet attached to the rotor for rotating therewith, and the second permanent magnet corresponds to the first permanent magnet with a flux gap formed therebetween.
 16. The liquid pump as described in claim 14, wherein the pump casing comprises a hollow main body, a top cover hermetically attached to a top end of the main body, and a bottom cover attached to a bottom end of the main body to form a receiving space between the partition wall and the bottom cover to receive the motor driving unit therein.
 17. A liquid pump, comprising: a pump casing comprising a liquid inlet, a liquid outlet below the liquid inlet and a receiving space therein; an impeller rotatably mounted in the receiving space, wherein when the impeller rotates liquid is driven to flow into the pump via the liquid inlet and out of the pump via the liquid outlet, a magnet attached to the impeller; a first pair of magnetic spacers mounted respectively on the impeller and the pump casing, the first pair of magnets being so positioned that a repulsive force exists therebetween, the repulsive force counteracting a downward force acting on the impeller during rotation of the impeller to drive the liquid to flow; and a motor driving unit interacting with the magnet attached on the impeller to drive the impeller to rotate.
 18. The liquid pump as described in claim 17, further comprising a second pair of magnetic spacers respectively mounted on the impeller and the pump casing, the second pair of magnetic spacers being so positioned that a repulsive force exists therebetween, the second pair of magnetic spacers being located above the first pair of magnetic spacers.
 19. The liquid pump as described in claim 18, further comprising a shaft, the impeller rotating around the shaft, the first pair of magnetic spacers surrounding a lower portion of the shaft and located below the impeller, and the second pair of magnetic spacers surrounding an upper portion of the shaft and located above the impeller.
 20. The liquid pump as described in claim 19, wherein the motor driving unit is located below the first pair of magnetic spacers. 